1. Field of the Invention
This invention relates to electronics enclosures.
2. Relevant Prior Art
For many years, in the manufacture of electronics enclosures, e.g. in the manufacture of frame or other equipment or steel shelves for housing printed circuit boards and circuit packs, the walls of the enclosures have been coated with zinc plating which has, in turn, been protected by a chromate conversion coating of varying thickness. The chromate protected zinc coating provided sufficient rust protection to the metal of the enclosures. A problem existed, however, with such enclosures. In order to ground the enclosures, it has always been necessary to employ beryllium copper gaskets between metal components, the gaskets having sharp spurs. When the metal components are secured together, the spurs cut into the metal to be held forcibly against bare metal surfaces thereby providing gas-tight connections for the passage of electrical current between the metal components thereby providing the grounding effect. The protection afforded by the chromate conversion coating over the zinc coating in localized areas is immediately destroyed by the forcing of the metal spurs through the metal surfaces. As a result, to prevent corrosion at those localized regions, it is then necessary to provide a localized protection which has, in the main, taken the form of a tin/lead solder applied to the enclosures. Hence, in forming the conventional enclosures, in order to provide certain electrical requirements, other problems have been created which need solving with further protective measures.
Electronics enclosures manufactured in the above manner have been satisfactory until the advent of electronic equipment which emits electromagnetic radiation thereby resulting in electromagnetic interference (EMI) which is found to effect the function of other electronic equipment. Electronics enclosures of the above general structure and made in the above manner are now being found to be sadly lacking in providing protection either for electronics equipment housed within the enclosures against EMI emanating from outside the enclosures or for equipment disposed outside the enclosures and against EMI originating inside the enclosures.